Custom S/390 G5 and G6 microprocessors

Compared with the G4 microprocessor, the S/390® G5 microprocessor contains many architectural and performance enhancements. The G6 microprocessor represents a technology performance improvement over G5, with system support for additional processors. The G5 processor uses IBM CMOS 6X technology and has a clock frequency of 500 MHz in its fastest models. The G6 uses CMOS 7S technology with a clock frequency up to 637 MHz. The processors include a new IEEE binary floating-point architecture and additional reliability-availability-serviceability (RAS) improvements. The processor has significant performance improvements, including a larger level-1 (L1) cache, enhancements to the instruction fetch buffers, a branch target buffer (BTB), enhancements for a number of instructions, a new quiesce mechanism for instructions that modify translation lookaside buffer (TLB) entries, and a new level-2 (L2) cache and memory subsystem.